Rail for ladder



Jana-7,1970 I H. w. STILLMAN, JR

RAIL FOR LADDER Filed Aug. 26, 1968 Era. 2 fie, 5

IN VEN T02 ?7varolcl 152%:

United States Patent 3,491,853 RAIL FOR LADDER Harold W. Stillman, Jr., Western Springs, Il]., assignor to Sears, Roebuck and Co., Chicago, 11]., a corporation of New York Filed Aug. 26, 1968, Ser. No. 755,026 Int. Cl. E06c /04 US. Cl. 182-207 9 Claims ABSTRACT OF THE DISCLOSURE A channel type rail especially suitable for ladders and having a cross-sectional configuration resembling the wellknown sigma shape, designed for economical production by extrusion, comprising generally J-shaped portions of which the usual channel flange constitutes the long leg of the I, the short foot being generally parallel to the long leg, a web portion of major width, and diagonal elements joining the web to each foot at obtuse angles. The free end portion of each flange is thickened, for improved mechanical advantage.

My invention relates to rails of the so-called channel type, which may have general application in the field of structural elements. My preferred application is for ladders, more particularly those having similar extensible sections, with transverse rungs attached to the rails, although adaptable for other purposes.

BACKGROUND OF THE INVENTION In the recent development of channel type rails for various applications in supporting loads, to withstand major torsional and bending stresses, considerable thought has been given to modified channels of the so-called sigma type, so designated because of its cross-sectional resemblance to the Greek letter of that name. It has been found in general that channels of this general design are capable of withstanding greater stresses and strains per unit weight of metal than a standard channel.

THE PRIOR ART A discussion on this subject may be found in an article by E. I. Stefanides, Sigma Section Optimises Beams Material Usage, Design News for June 24, 1964, Cohners Publishing Co., Inc.

An early form of said design is disclosed in Carnegie Steel Company Shane Book, 9th ed. 1923, page 51, as Tire Channel C 630.

Numerous patents have been issued on variations of said design, a recent one of which is to Kimpton No. 3,194,408, showing an adaptation of the sigma design to a storage rack and beam. A number of references cited against Kimpton show other adaptations of the basic design.

GENERAL OUTLINE OF THE INVENTION A particular object of my invention in this relatively well-developed art is to provide a new and improved beam following the broad general concept of the sigma design modified to be especially suitable for extrusion techniques, utilizing a relatively inexpensive and lightweight metal such as aluminum, which beam will be applicable for use as a ladder rail or upright as Well as other applications.

Still another object is to provide a rail of the character referred to having maximum strength-to-weight ratios,

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especially with regard to twisting or torsional strains, as compared with the conventional channel or even as compared with the usual or known sigma type of channel. Thus, my improved rail has a minimum of thickness and does not risk web buckling because of various reenforcement elements which I introduce in my novel design. Furthermore, the web configuration of my improved design reduces possibility of racking of the section by reason of stiffening of my improved rail at the rung connections, despite reduction of thickness of the web portion.

Furthermore, reduction of web material permits concentration of more metal in the flange portions of the rail, resulting in increased strength in the major direction as compared to a conventional I-beam, and a substantial increase in strength in the minor direction.

BRIEF DESCRIPTION OF THE DRAWINGS Referring now to the drawings forming a part of this specification and illustrating a preferred embodiment of my invention,

FIG. 1 is a cross-sectional, perspective view of a rail constituting one embodiment of my invention.

FIG. 2 is a fragmentary elevation of a pair of such rails as employed in an extensible ladder.

FIG. 3 is a similar view of a pair of such rails in a different ladder construction.

FIG. 4 is a cross-section taken substantially along line 4-4 of FIG. 2, and

FIG. 5 is a similar section taken substantially along line 5-5 of FIG. 3.

DETAILED DESCRIPTION FIGS. 2-5 show two versions of extensible ladders L and L to which my invention is applicable. As previously stated, my invention has other applications.

A pair of rails 10 (only one of which is shown) is arranged in parallel relation, connected by transverse steps or rungs R attached to rails 10 as by bolts, swaging, adhesive or welding, while a pair of generally similar rails also connected by similar members, is arranged in sliding nested relation with rails 10 as seen in FIG. 4. Aside from this basic construction, it is not considered necessary further to describe the ladder, as my invention is directed primarily to the rail structure.

FIGS. 3 and 5 illustrate a different arrangement for mounting a pair of ladder sections in slidable extensibility. In this arrangement, instead of being nested, a bracket B is bolted to one ladder section and has achannel portion C slidably embracing adjacent flanges of the rails.

Turning now to FIG. 1, the rail shown here is, in general, a sigma form of channel having a pair of generally parallel flange members 12, 12 and a substantially planar web portion 15 disposed between said flange members. preferably, a pair of parallel spaced apart stiffening ribs 18 extent longitudinally on opposite sides of web portion 15.

Web portion 15 is of a width substantially greater than one-half the overall width of the section, and may be as much as two-thirds of said width.

The free outer end portion 11 of flanges 12 are substantially thickened for a substantial distance inwardly of the outer edge thereof, in order to provide increased torsional strength and side strength at these points of the rail.

It will also be noted that said flange portions 12 vary in thickness from the free outer edge to the inner edge thereof, in order to provide optimum cantilever strength in said flange portions.

Thus, flange portions 12 comprise an inner section a, an outer section b, both of these sections being substantially the same width and substantially the same thickness and being connected by a section c tapering in thickness, intermediate section being of substantially equal width to sections a and b.

Extending normally from each flange 12 is a relatively short element 20 approximately equal in length to any one of flange sections a, b and c. Said element 20 is tapered in thickness from a maximum thickness at its juncture point with flange section a approximately equal to the thickness of section a and thence slightly diminishing to its juncture point with a relatively short foot portion 22 extending normally from element 20 or generally parallel to flange 12. It will be noted that foot 22 is of approximately the same length as flange section a, although approximately one-half the thickness thereof.

Thus, the combination of flange 12, element 20 and foot 22 forms a unit approximately J-shaped in crosssection.

A diagonally sloping element 25 connects web portion 15 and foot 22 at obtuse angles which are approximately equal at said juncture points, being approximately 120 at each point.

Foot 22, sloping element 25 and web portion 15, it will be noted, are approximately uniform in width, said width being substantially less than any portion of flange 12 and element 20. This reduction in thickness not only makes for a saving of metal and consequent lowering of cost but also contributes toward an increase in strength in the major direction of the rail as compared to a conventional I-beam and a substantial increase in strength in the transverse or minor direction.

It will be understood that while I have shown, for convenience of illustration, the various elements of the beam joining adjacent elements at a sharp angle, e.g., the junctures between elements 22 and 25 and between element 25 and web 15, a small radius of curvature may be employed at these juncture points rather than sharp angles. In any event, as stated hereabove, my improv'ed design is especially adapted for production by extrusion methods. Furthermore, this design is likewise highly suitable for telescopic arrangement, allowing the use of rungs of substantially equal length on both top and bottom sections of an extension ladder.

For optimum mechanical advantages, it is desired that the plane of web 15 be disposed approximately in line with the inner edge of flange sections b, i.e., spaced inwardly of the free edges of the flanges about one-third the width thereof.

Referring now to the rails shown in section in FIG. 4, it will be noted that the flanges 12a also form part of a J-shaped end section and have a thickened free outer portion b, similar to the rail shown in FIG. 1.

Another version is seen in FIG. 5, where flange 12b has a free edge portion b" projecting transversely from the plane of flange 12b, to accomplish a similar mechanical effect.

Web portions 15 (FIG. 4) and 15 (FIG. 5) also are, as in FIG. 1, of substantial length compared to the overall width of the rail, about one-half in FIG. 4 and approximately twothirds in FIG. 5.

Various changes coming within the spirit of my invention may suggest themselves to those skilled in the art; hence, I do not wish to be limited to the specific embodiments shown and described or uses mentioned, but intend the same to be merely exemplary, the scope of my invention being limited only by the appended claims.

I claim:

1. A channel rail especially suitable for ladders, being of generally sigma cross-sectional shape and comprising (a) a spaced pair of generally parallel, generally J- shaped portions each consisting of an outer flange, a

short foot generally parallel to said flange, a relatively short element connecting said flange and foot and normal thereto, and a projection on said outer flange at the portion thereof remote from said short foot and opposite said last-mentioned element,

(b) a web portion normal to said flanges and of substantial width compared to the overall width of the rail, and

(c) a diagonally sloping element connecting each foot with said web portion at obtuse angles.

2. A rail as in claim 1, wherein said projection on each outer flange at the free end portion thereof is of creased thickness as compared with the adjacent portion thereof, said increased thickness being opposite said short element and extending for a substantial length transversely of the major axis of the rail.

3. A rail as in claim 2, wherein said web, sloping element and foot are relatively thin as compared with the remainder of said J-shaped portions.

4. A rail as in claim 2, having at least one rib extend ing longitudinally of said web intermediate the longitudinal edges thereof.

5. A channel rail especially suitable for ladders, being of generally sigma cross-sectional shape and comprising (a) a spaced pair of generally parallel, generally I- shaped portions each consisting of an outer flange, a short foot generally parallel to said flange and a relatively short element connecting said flange and foot and normal thereto,

(b) a web portion normal to said flanges and of substantial width compared to the overall width of the rail,

(0) a diagonally sloping element connecting each foot with said web portion at obtuse angles, and

(d) each of said flanges comprising a relatively thick free end, an inner end portion and an intermediate portion tapering to a reduced thickness at its juncture with said free end portion, said foot being relatively thin, and the element connecting the flange and foot for its major extent having a thickness of the order of the thicker portions of said flange.

6. A rail as in claim 5, wherein said flange portions are of approximately equal width.

7. An extension ladder embodying longitudinally ex 0 tending channel rails of generally sigma cross-sectional shape and comprising (a) a pair of said channel rails in juxtaposed relation adapted for relative reciprocating movement,

(b) each of said rails comprising a pair of generally parallel, generally J-shaped portions each consisting of an outer flange, a short foot generally parallel to said flange, a relatively short element connecting said flange and foot and normal thereto, and a projection on said outer flange at the portion thereof remote from said short foot and opposite said lastmentioned element,

(0) a Web portion normal to said flanges and of substaiitial width compared to the overall width of the tar,

(d) a diagonally sloping element connecting each foot with said web portion at obtuse angles, and

(e) means for interconnecting the abutting outer flanges of the J-shaped portions in juxtaposition to each other for guiding said channels in their relative reciprocating movement.

8. A device as set forth in claim 7, wherein said lastmentioned means comprises the projection on the outer flange of the J-shaped portion on one rail, of substantial 'width and thickness, nested within the space defined by the outer flange, short food and normally extending connecting element of the juxtaposed J-shaped portion of the companion rail.

9. A device as set forth in claim 7, wherein said lastmentioned means comprises a bracket affixed to the web portion of one of said rails with the free end thereof ex- 5 6 tending laterally beyond the outer flange of the J-shaped 3,037,593 6/ 1962 Webster 52-730 portion thereof, said bracket having a guide slot therein 3,194,408 7/1965 Kimpton 52720 for accommodating the outer flange of the J-shaped portion and the projection extending transversely therefrom FOREIGN PATENTS appurtenant to the juxtaposed channel rail. 5 1446855 6/1966 France References Clted REINAL'DO P. MACHADO, Primary Examiner UNITED STATES PATENTS 2,144,293 1/1939 Hull 182219 2,508,032 5/1950 Kennedy 52-729 10 18246 

